A lot of missionaries rely (unfortunately in my opinion) on web-based mail services. I say unfortunately because many missionaries live in Internet-slow countries and they spend countless hours waiting for pages to reload. Using Outlook, Outlook Express or Thunderbird is a much better solution, and a couple of the below solutions give you that flexibility.
If you're going to use a web-based mail service, why not use the best? Last month TechCrunch compared the top three mail services, Hotmail, Gmail & Yahoo.
Overall we prefer Gmail over all other webmail applications because performance (speed) is consistently fast, and emails can be tagged making search much more effective. They also offer more storage and other features, and it’s free. However, Yahoo and Live Hotmail offer more mainstream Outlook-like user interfaces (although Live Hotmail does not allow you to access other email accounts from their application), whereas Gmail takes some time to get used to. If you are looking for speed and tagging is important, Gmail is for you. If you are looking for the closest thing to Outlook online, go with Yahoo Mail.
Read the post for more details.